Timing circuitry incorporating radioactive batteries



S. WALLACK Aug. 10, I965 Filed NOV. 9, 1955 INVENTOR. STANLEY WALLACK ATTORNEY United States Patent 0 3,2lll),300 TIMENG QIRQUITRY INCORPGRATING RADIOACTIVE BATTERIES Stanley Wallach, Jackson Heights, N.Y., assignor to Leesona Corporation, Warwick, 11.1., a corporation of Massachusetts Filed Nov. 9, 1955, Ser. No. 545,953 9 tClaims. (Cl. 317-441) This invention relates to electrical control apparatus, and in particular to timing circuitry incorportating radioactive batteries to provide a reliable control for associated equipment.

Within recent years, batteries employing radioactive elements for developing relatively high voltages at low current values have been introduced to the art. These batteries offer several advantages in operational characteristics which establish them as highly satisfactory potential sources in certain electronic and electrical applications. For example, radioactive batteries have a shelf life of the order of 25 years, do not contain any moving parts, are independent of ambient conditions, and can be economically fabricated in miniaturized form. Moreover, the radioactive materials required for their fabrication are readily available as by-products of pile operation.

In view of the fact that the electrical characteristics of these batteries are in many aspects unique and not directly comparable :to other types of electrical generators in the art, appropriate circuit design for a particular application must necessarily be adapted to the characteristics of radioactive batteries.

The present invention features an electrical control device incorporating in a preferred embodiment a pair of radioactive batteries as the necessary energy sources to eliect circuit operation. The circuitry is uniquely adapted to the characteristics of the radioactive batteries so that a timed control operation is provided that is fail safe. This device can be advantageously employed, for example, to arm or detonate demolition devices such as projectiles and mines.

A principal object of this invention is to provide a control device having a very high degree of reliability and which is tall safe in the event that the remote possibility of failure should occur. The reliability of the subject control is directed not only to the proper performance of the desired event :at the termination of an accurately timed interval, but also includes a predictable and accurate subdivision of the overall timing interval whereby programming of events preliminary to the desired event can be effected. The type of fail safety herein contemplated is directed to the accomplishment of the desired event or an alternative event either immediately or after a short time interval, if for any reason the normal :sequence of operation of the components of the control is interrupted or terminated.

Another object of this invention is to provide a control device adapted to program a relatively large number of desired operations during a control time interval having essentially no upper time limit.

Another object of this invention is to provide a control' device which may be readily tested as to operability and timing interval prior to use.

Another object of this invention is to provide a control device which may be easily and economically fabricated in miniaturized form with self-contained permanent energizing sources. 1

A preferred embodiment of this invention contemplates a timing unit energized by a first radioactive battery, and a fail safe circuit connected to said timing unit and energized by a second radioactive battery.

The timing unit comprises a voltageregulated power supply including a radioactive battery which periodically energizes an impulse counter by a timed sequence of pulses applied from a timing network connected to the output of the power supply. The impulse counter prefera'bly has at least a pair of contacts in which one of said contacts is actuated in response to each energizing pulse applied to the counter and the other of the contacts is actuated in response .to a predetermined number of energized pulses applied to the counter.

In the specific application of the foregoing timer to sterilize a demolition mine by disarming the mine, the clo sure of first of said contacts, for example, may be employed to program intermittent active periods or the like, and the closure of the second of said cont-acts may be employed to provide permanent disarming.

The fail safe circuit which is connected to the timer unit comprises a second unregulated power supply having a capacitor filter section charged by a second radioactive battery. The output of this power supply is applied to a relay through a gas diode. This relay actuates a contact which in one application shunts the second of said counter contacts thereby providing an alternative ararngement for effecting control operation. The relay contact is not operative, however, so long as the counter is periodically actuated. This result is attained for the reason that the first of said counter contacts periodically shorts the output of the second power supply at a frequency sufiiciently great to prevent the capacitor filter from charging to an operate potential for said relay.

In order that all of the features for attaining the objects of this invention may be readily understood, detailed reference is herein made to the accompanying drawing wherein a schematic circuit diagram of a preferred embodiment of the control apparatus of this invention is shown.

Referring now to the drawing, battery 1 is a radioactive battery providing a high-voltage output of the order of several thousands of volts at low current. The output potential of radioactive battery is generated from the electrical energy associated with charged particles that are emitted by a local source of radioactive material. In general, this is accomplished by placing a collector electrode or electrodes adjacent the supply of radioactive material to collect the charge particles, thereby developing an electrical potential between the radioactive material and the collector electrode. Battery 1 may correspond in construction to the batteries disclosed in the copending application of H. C. Li-eb and E. J. Dziedziula Serial No. 470,565, filed November 23, 1954, now U.S. Patent 2,774,891 issued December 18, 1956 and theapplication of H. C. Lieb Serial No. 470,566, filed November 23, 1954, now U.S. Patent 2,930,909 issued March 29, 1960. Other constructions are also disclosed in U.S. Patents 2,517,120, 2,552,050 and 2,555,143, all issued to E. G. Linder on August 1, 1950, May 8, 1951, and May 29, 1951, respectively.

The output of battery 1 is directly shunted by capacitor 2, and therefore the low current output of the battery slowly charges this capacitor to the battery output potential. Battery 1 and capacitor 2 are directly shunted by serially-connected gas diode 3 and resistor 4.

Components 1 through 4 comprise a voltage-regulated power supply whose output voltage is determined in the main by the firing potential of gas diode 3. Radioactive battery 1 is incapable of supplying a relatively large current at a constant voltage and therefore components 2, 3 and 4 are connected across the output in order to apply a relatively constant potential to serially-connected capacitor and resistor 6.

In particular, radioactive battery 1 supplies energy at a very low current level to charge capacitor 2. As the potential across battery 1 and capacitor 2 builds up and approaches the firing potential of gas diode 3, the resistance of said diode decreases sufiiciently to permit a minute flow of current to pass through diode 3 and resistor 4. Resistor 4 has a very high resistance value, preferably of the order of several megohms, in order to prevent the firing of diode 3 and to maintain the diode at approximately the threshold of the firing point. As a result of the minute flow of current, the voltage across battery 1, capacitor 2, and serially connected diode 3 and resistor 4 attains equilibrium at a value below the firing voltage of the diode. This voltage regulation is attained because any incremental increase in battery potential will merely tend to cause an increased fiow of current through diode 3 and resistor 4 which prevents any further increase in output potential.

The voltage regulated output potential of the foregoing power supply components charges capacitor 5 by current minals in, or an alternativeevent, either immediately flow through resistor d. The value of resistor 6 is such that capacitor 5 will charge to the firing voltage of gas diode 7 in a predetermined time interval. Obviously the time required to charge said capacitor 5 to the firing voltage of diode 7 can'be increased by increasing the value of resistor 6 and can be decreased by decreasing said value.

The potential appearing across charge capacitor 5 may either be applied to gas diode 7 through resistor 8 or through the actuating winding 9 of impulse counter '10 depending upon the operative positioning of manually operated switch section 11a of switch 11.

The resistancevalue of resistor 8 is so selected that in the event switch section 11a assumes the position shown in the drawing, the potential applied to gas diode 7 is less than the firing potential.

In'the event switch section 11a is elevated into contact 7 with the upper terminal of winding 9, the relatively low impedance of this winding permits the application of a firing potential to gas diode 7 by charged capacitors.

The resulting current-pulse flowing through winding 9 of' impulse counter 10 momentarily actuates contact 12 of the counter. Contact 12 is so incorporated within counter 10 that momentary closure thereof is efiected in response to the flow of each current-pulse through counter winding 9. Counter contact 13, on the other hand, is actuated only after a predetermined number of pulses have been applied to and registered by counter 10. For example, in response to the appropriate setting of mechanisms the design of which is well-known within the counter art, the closure of contact 13 may be set to occur only after the application of say 10,000 pulses to counter 10. It should be understood, of course, that contact 12 will momentarily close in response to each of the appliedpulses to the counter.

Terminals 16 are connected to counter switch 13 through switch section 1112 which is mechanically ganged to switch section 11a for simultaneous operation therewith. It is contemplated that terminals 16 will be connected to associated apparatus (not shown) which is to be actuated into a desired operative condition in response to the closure of counter contact 13 after the predetermined number of pulses have been applied to the counter.

Briefly stated, the structure thus far described comprises a timing unit for periodically actuating counter llll in response to the application of an accurately timed sequence of applied pulses to winding 9. In order to tion.

or after a short time interval, if for any reason the normal sequence of operation of the components of the control is interrupted or terminated.

In particular, radioactive battery 2 9, corresponding in construction to radioactive battery 1, is directly shunted by capacitor 21 whereby the capacitor is slowly charged by current flow from the battery. The winding of relay 7 22 is connected directly across battery 20 and capacitor 21 in the event that switch section Me, which is ganged for simultaneous movement with sections Illa and 11b, assumes the position shown in the drawing. With this switch positioning, the relatively lowimpedance of the winding of relay 22 effectively shunts battery Ziiand capacitor 21 whereby sufficient potential cannot be attained to operate relay 22.

In the event that switch section lie is operated so as to connect gas diode 23 to the winding of relay 22, the overall series impedance now presented to battery 20 and capacitor 21 is sufficiently high to permit capacitor 21 to charge sufficiently to apply a firing potential to gas diode 23. The resulting firing of diode 23, permits the application of an operate current pulse through the winding of relay 22 which close-s the associated normally open contact 25. a

Contact 25 is connected directly'across the terminals of counter contact 13 in the event that manually operated switch 26 assumes the position shown in the drawing. It should be noted that a closed circuit can be presented to terminals 16 by either counter contact 13 or contact 25 of relay 22. Y e

, Radioactive battery 20, capacitor 21 and gas diode 23 are selected so that the time interval necessary to charge capacitor 21 to the firing voltage of diode 23 is greater than the time interval necessary to charge capacitor 5 to the firing voltage of diode 7. In the usual application, the closure of counter contact 13 will be required to effect the occurrence of a desired event in response to a predetermined count number in counter ltl. Contact 25 is so connected that it can simulate the desired predetermined count in counter 10, thereby producing the same desired event with respect to the equipment connected to terminals 16 in the event the timer fails .to actuate counter 10. If the timing unit is operating satisfactorily so as to periodically apply the desired sequence of pulses to counter 10, relay 22 is maintained in an unoperated condition for the reason that the periodic closure of counter contact 12 in response to each count effectively shorts the output terminals of battery 20 and capacitor'21 to discharge said capacitor before the firing voltage of diode 23 is reached thereby preventing capacitor'21 from charging sufficiently to operate relay 22.

Relay 22 is operated only in the event that circuit malfunctioning occurs so that counter contact 12 is not periodically closed as required by proper circuit opera- If counter contact 12 fails to periodically close, capacitor 21 is uninterruptingly charged by battery 20 to a firing potential for diode 23 whereby relay 22 is operated.

Contact 25 is shunt connected across the terminals of counter contact 13 through switch 26 so as to provide fail safe operation in the sense that circuit malfunctioning will bring about a premature occurrence of the event desired from the equipment connected to terminals 16. In the event; however,- that an alternative operation is desired in response to equipment failure, switch 26 may be manually operated so as to connect contact 25 to terminals 28. Auxiliary equipment (not shown) connected to ter- 5 minals 28 may thereby be actuated by the fail safe circuitry.

The detailed operation of the foregoing control circuitry to sterilize a demolition device, such as a land mine, by explosion is as follows:

The detonation circuit (not shown) of such a mine is connected to terminals 16 so as to be completed in response to the closure of counter contact 13. Counter 10 is manually set to the desired predetermined count number which is required to actuate counter contact 13.

In the event that the type of fail safety required is that which will result in the premature explosion of the mine in case of circuit malfunctioning, control switch 26 is positioned as shown in the drawing so that counter contact 13 is shunted by normally-open relay contact 25. if an alternative event other than premature explosion is desired in response to circuit failure, the equipment which is to effect this alternative event is connected to terminals 28 and switch 26 is positioned to terminal 27, thereby presenting a closed circuit to terminals 28 in response to the closure of contact 25. If a programming operation is desired preliminary to the actual explosion of the mine, switch 12 can be mechanically connected as, for example, by means of a cam or other linkage (not shown) to suitable auxiliary equi ment whereby the movement of switch 12 will activate said auxiliary equipment.

Initially the switch 11 comprising sections limb-0 is positioned in a non-operate position shown in the drawing. With this circuit connection, the power supply comprising radioactive battery 1 will maintain capacitor 5 at a potential very slightly below the firing potential for gas diode 7. Counter 16 is, of course, unoperated for the reason that switch section 11a is so positioned as to open the energizing circuit for counter winding h.

The power supply comprising radioactive battery 2t) assumes a relatively low output voltage inasmuch as the switch section 110 connects low impedance relay winding 22 directly across the output of this power supply. The

resulting voltage is substantially below the operate voltage required for relay 22.

The circuit remains in equilibrium at the foregoing circuit conditions until such time as switch 11 is driven to its other positioning. With this occurrence and after the short period of time required for the voltage across capacitor 5 to rise to the firing voltage of diode 7, capacitor 5 discharges through diode 7 and winding 9 thereby actuating the counter and causing a momentary closure of counter contact 12 only. During this operation, capacitor 2 remains at the regulated voltage determined by diode 3. After the firing of diode 7, the voltage appearing across capacitor 2 causes capacitor 5 to charge at a rate determined by the time constant R C After the proper time interval has elapsed, which may in the usual instance be of the order of 24 hours, capacitor 5 is again charged to the firing voltage of diode 7 whereupon capacitor 5 discharges through diode 7 and winding 9 again actuating the counter.

The above sequence is uninterruptingly repeated until the termination or" the sterilization delay period determined by the initial predetermined setting of counter 16. At this time counter contact 13 is closed, and this switch closure completes the detonation circuit for the land mine connected to terminals 16 through closed switch section 11b thereby resulting in sterilization.

The'reason for the inclusion of components 2 through 6 in the circuitry herein should be noted at this time. While it is true that radioactive battery 1 could readily be made to directly charge capacitor 5 repetitively to the tiring potential of gas diode 7 thereby eventually resulting in sterilization, such an arrangement would, however, result in a pulse interval which is inversely proportional to the radioactive current of battery 1. That is, inasmuch as battery 1 utilizes an element such as, for example, the radioisotope Strontium 90, which has a shelf- 6 life of approximately 25 years, the pulse time interval at the end of this period would be exactly twice its initial value. The addition of the aforementioned components results in circuit operation independent of the value of the radioactive current output of battery 1.

As previously mentioned, the additional circuitry comprising the power supply energized by radio-active battery 20 and also relay 242 provides fail safety which will re suit in the premature detonation of the mine connected to terminals in in the event of malfunctioning of the timing unit. At the time that the switch comprising sections 1=llab-c is manually operated to initiate the timing operation, switch section 110 in particular removes the eifective short applied by the low impedance winding of relay 22 from the output of the power supply comprising radioactive battery 2t). Components 2%, 21, 22 and 2-3 are so elected that capacitor 21 will be charged to the firing voltage of diode 23 preferably in a time interval approximately 50 percent greater than the time interval occurring "between successive closures of counter contact 12. If capacitor 21 is charged this full time inter-val, capacitor 21 will discharge through gas diode 23 into the winding of relay 22, thereby closing contact 25 and sterilizing the mine connected to terminal 16. However, it should be emphatically noted that this circuit action is attained only in the event of failure in some other portion of the circuit; because during normal operation, counter contact 12 is momentarily closed during each pulse through counter it thereby shorting capacitor 2-1 and starting the charging cycle therefor once again. Accordingly, the fail safe circuitry checks both the electrical and mechanical operation of the timing unit.

The power supply comprising battery 2% does not include components directed to voltage regulation for the reason that precise timing intervals are not required, and a gradual increase in the interval of time required to charge capacitor 21 to a given value is of relatively minor consequence.

t is to be understood that the above-described arrangement is illustrative of the application of the principles of this invention. Numerous other arrangements may be devised by those skilled in the art without departing from the scope of the invention.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

ll. Control apparatus comprising a voltage-regulated power supply including a radioactive battery, an impulse counter having at least a pair of contacts in which one of said contacts is actuated in response to each energizing pulse applied to the counter and the other of said contacts is actuated in response to a predetermined number of energizing pulses applied to said counter, a relay actuatmg a contact, a timing network including a serially-connected resistor and capacitor shunting the output of said power supply and a gas tube connected to the junction connection for said resistor and capacitor, a second power supply including a radioactive battery and a capacitor shunting said battery, an actuating switch having a first switch section operable to connect the output of said tuning network at said gas tube to said counter thereby applying a sequence of timed pulses to said counter and a second switch section operable to connect said relay to the output of said second power supply, said first counter contact shunting the output of said second power supply during each closure thereby preventing the build-up and application of an operate potential to said relay so long as said counter is periodically actuated, a pair of conductors connected to said second contact for efifecting programming in response to a count of said predetermined number, and a third pair of output conductors .connectedto said relay contact for effecting fail safe programming in response to an interruption in the periodrc actuation of said firs-t contact.

2. Control apparatus comprising a voltage-regulated power supply including a radioactive battery, an impulse counter having at least a pair of contacts in which one '2? of said contacts is actuated in response to each energizing pulse applied to the counter and the other of said contacts is actuated in response to a predetermined number of energizing pulses applied to said counter, a relay actuating .a contact shunting said other counter contact, a timing network connected to the output of said voltageregulated power supply, a second power supply including a radioactive battery, a gas diode, and an actuating switch having a first switch section operable to connect the output of said timing network to said counter thereby applying a sequence of timed pulses to said counter and a second switch section operable to connect said relay to the output of said second power supply through said gas diode, said first counter contact shunting the output of said second power supply during each closure thereby preventing the buildup and application of an operate potential to said relay so long as said counter is periodically actuated whereby said other counter contact is operatively eiiective to control a circuit in response to said predetermined number of pulses being applied to said counter.

3. Control apparatus comprising a power supply, an impulse counter having at least a pair of contacts in which one of said contacts is actuated in response to each energizing pulse applied to the counter and the other of said contacts is actuated in response to a predetermined number or" energizing pulses applied to said counter, a relay actuating a contact shunting said other counter contact, a timing network connected to the output of said power supply, a second power supply, a nonlinear impedance element, and an actuating switch having a first switch section operable to connect the output of said timing net-work to'said counter thereby applying a sequence of timed pulses to said counter and a second switch section operable to connect said relay to the output of said second power supply through said non-linear impedance element, said first counter contact shunting the output of said second power supply during each closure thereby preventing the build-up and application of an operate potential to said relay so long as said counter 1s periodically actuated whereby said other counter contact is operatively elfective to control an output circuit tlIl response to said predetermined number of pulses being applied to said counter.

4. Control apparatus comprising a power supply including a radioactive battery, an impulse counter having at least a pair of contacts in which one of said contacts is actuated in response to each energizing pulse applied to the counter and the other of said contacts is actuated in response to a predetermined number of energizing pulses applied to said counter, a relay actuating a contact, a timing network connected to the output of said power supply, a second power supply including a radioactive battery, and means operable to connect the outputof said timing network to said counter thereby applying a sequence of timed pulses to said counter and to connect said relay to the output of said second power supply, said first counter contact shunting the output of said second power supply during each closure thereby preventing the build-up and application of an operate potential to said relay so long as said counter is periodically actuated whereby said other counter contact is operatively effective to control an output circuit in response to said predetermined number of pulses being applied to said counter. Y

5. Control apparatus comprising a power supply including a radioactive battery, an impulse counter having a contact which is actuated in response to each energizing pulse applied to the counter, switching means, a timing network connected to the output of said power supply, a second power supply'including a radioactive battery, and means operable to connect the output of said timing network to said counter thereby applying a sequence of timed pulses to said counter and to connect said switching means to said second power supply, said counter contact effecting a discharge of said second power supply during each closure thereby preventing the build-up and application of an operate potential to said switching means so long as said counter is periodically actuated.

6. Control apparatus comprising'a power supply including a radioactive battery, impulse responsive means including switching means which is actuated in response to each energizing pulse applied to said impulse responsive means, a networkconnected to the output of said power supply and translating this output into one or more pulses, secondswitching means, a second power supply including a radioactive battery, and means operable to connect the output of said network to said impulse responsive means thereby applying one or more pulses to said impulse responsive means and to connect said second switching means to the second power supply, said first switching means when actuated effecting a discharge of said second power supply thereby preventing the build-up and application of an operate potential to said second switching means so long as said impulse responsive means is actuated at a time interval less than that required for the second power supply to develop suiiicient potential to apply an operate potential to said second switching means.

7. Control apparatus comprising a power source, impulse responsive means including switching means which is actuated in response to each energizing pulse applied to said impulse response means, a network connected to an output of said power source and translating this output into one or more pulses, second switching means, a second power source, and means connecting said network to said impulse responsive means thereby applying one or more pulses to said impulse responsive means and connecting said second switching means to the second power supply, said first switching means when actuated effecting a discharge of said second power supply thereby preventing the build-up and application of an operate potential to said second switching means.

8. Control apparatus comprising a voltage-regulated power supply including a radioactive battery, impulse responsive means including switching means which is actuated in response to each energizing pulse applied to said impulse responsive means, a timing network including a serially-connected resistor and capacitor shunting the output of said power supply and a gas tube connected to the junction connection for said resistor and capacitor, a second switching means, a second power supply including a radioactive battery and a capacitor directly shunting said battery, and means operable to connect the output of said network at said gas diode to said impulse responsive means thereby applying one or more pulses to said impulse responsive means and to connect said second switching means to the second power. supply, said first switching means when actuated effecting a discharge of said second power supply thereby preventing the build-up and application of an operate potential to said second switching means so long as said impulse responsive means is actuated at a time interval less than that required for the second power supply to develop sufiicient potential to apply an operate potential to said second switching means.

9. Control apparatus comprising a power supply including a radioactive battery, impulse responsive means including a pair of switching means the first of which is actuated in response to each energizing pulse applied to said impulse responsive means and the second of which is actuated in response to a predetermined number of energizing pulses applied to said impulse responsive means, a timing network connected to the output of said power supplyand translating this output into a sequence of pulses, a second power supply including a radioactive battery, third switching means, and means connecting the output of said timing network to said impulse responsive means thereby applying one or more pulses to said impulse responsive means and connecting said third switching 9 means to said second power supply, said first switching means when actuated effecting a discharge of said second power supply thereby preventing the buildup and application of an operate potential to said third switching means so long as said impulse responsive means is actuated at 5 a time interval less than that required for the second power supply to develop sufficient potential to apply an operate potential to said third switching means, said second switching means being operative to control a 10 mined number of pulses being applied to said impulse response means, said third switching means being operative to control an output circuit connected thereto in response to an interruption in the periodic actuation of said first switching means.

No references cited.

SAMUEL BERNSTEIN, Primary Examiner.

circuit connected thereto in response to said predeter- 10 CHESTER L. JUSTUS, Examiner. 

1. CONTROL APPARATUS COMPRISING A VOLTAGE-REGULATED POWER SUPPLY INCLUDING A RADIOACTIVE BATTERY, AN IMPULSE COUNTER HAVING AT LEAST A PAIR OF CONTACTS ON WHICH ONE OF SAID CONTACTS IS ACTUATED IN RESPONSE TO EACH ENERGIZING PULSE APPLIED TO THE COUNTER AND THE OTHER OF SAID CONTACTS IS ACTUATED IN RESPONSE TO A PREDETERMINED NUMBER OF ENERGIZING PLUSES APPLIED TO SAID COUNTER, A RELAY ACTUATING A CONTACT, A TIMING NETWORK INCLUDING A SERIALLY-CONNECTED RESISTOR AND CAPACITOR SHUNTING THE OUTPUT OF SAID POWER SUPPLY AND A GAS TUBE CONNECTED TO THE JUNCTION CONNECTION FOR SAID RESISTOR AND CAPACITOR, A SECOND POWER SUPPLY INCLUDING A RADIOACTIVE BATTERY AND CAPACITOR SHUNTING SAID BATTERY, AN ACTUATING SWITCH HAVING A FIRST SWITCH SECTION OPERABLE TO CONNECT THE OUTPUT OF SAID TIMING NETWORK AT SAID GAS TUBE TO SAID COUNTER THEREBY APPLYING A SEQUENCE OF TIMED PULSES TO SAID COUNTER AND A SECOND SWITCH SECTION OPERABLE TO CONNECT SAID RELAY TO THE OUTPUT OF SAID SECOND POWER SUPPLY, SAID FIRST COUNTER CONTACT SHUNTING THE OUTPUT OF SAID SECOND POWER SUPPLY DURING EACH CLOSURE THEREBY PREVENTING THE BUILD-UP AND APPLICATION OF AN OPERATE POTENTIAL TO SAID RELAY SO LONG AS SAID COUNTER IS PERIODICALLY ACTUATED, A PAIR OF CONDUCTORS CONNECTED TO SAID SECOND CONTACT FOR EFFECTING PROGRAMMING IN RESPONSE TO A COUNT OF SAID PREDETERMINED NUMBER, AND A THIRD PAIR OF OUTPUT CONDUCTORS CONNECTED TO SAID RELAY CONTACT FOR EFFECTING FAIL SAFE PROGRAMMING IN RESPONSE T AN INTERRUPTION IN THE PERIODIC ACTUATION OF SAID FIRST CONTACT. 